Amino acid adsorption on hydrophilic TiO2: A sum frequency generation vibrational spectroscopy study

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Abstract

Sum frequency generation vibrational spectroscopy (SFG) is a powerful tool for in situ investigation of adsorption processes at biologically important solid-liquid interfaces. In this work adsorption of different amino acids was investigated by SFG at the titanium-dioxide-amino acid solution interface. While both naturally occurring acidic amino acids, aspartic acid and glutamic acid, were found to form an ordered adsorbate layer, amino acids with non-acidic side chains exhibited little affinity towards TiO2. A detailed study of aspartic acid on TiO2 pointed out that both carboxylic groups of the molecule are coordinated to the surface; data taken in the carboxyl stretching frequency range revealed that one of them is bonded monodentally to a surface Ti ion, while the other is most probably stabilized by a hydrogen bond. The results indicate that the acidic side chain is the prerequisite of the formation of a stable, ordered amino acid adsorbate layer on TiO2.

Original languageEnglish
Pages (from-to)48-56
Number of pages9
JournalVibrational Spectroscopy
Volume50
Issue number1
DOIs
Publication statusPublished - May 26 2009

Keywords

  • Adsorption
  • Amino acid
  • Carboxyl stretch
  • Sum frequency generation
  • Titanium-dioxide

ASJC Scopus subject areas

  • Spectroscopy

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